Because a UHF band RFID system is capable of collectively reading a plurality of RFID tags and is also capable of miniaturizing the RFID tags, the UHF band RFID system has been spreading in various fields including retail business.
Conventionally, as this kind of RFID tag, for example, one described in Patent Document 1 (identified below) is known. Specifically, Patent Document 1 discloses a configuration in which a loop electrode is sandwiched between insulating sheets, and the insulating sheets are attached to a metal surface in a tack index manner so that and the loop electrode is oriented perpendicular to the metal surface.
Patent Document 1: Japanese Patent No. 5136538
However, in the configuration of Patent Document 1, there is a problem that relative positions of the metal surface and a loop surface of the loop electrode are unstable due to deterioration of strength of a support member of the insulating sheet over time. When the loop surface is tilted from a state perpendicular to the metal surface, intensity of an electric field induced from a magnetic field generated by the loop electrode decreases, and gain of an antenna decreases. That is, unless the relative relationship between the metal surface and the loop surface is stable, communication characteristics will fluctuate.